1. Field of the Invention
The present invention relates to a multilayer printed circuit board in which a plurality of conductive layers are electrically connected to each other through bumps, and to a method for manufacturing the multilayer printed circuit board.
2. Description of the Related Art
As a method of manufacturing a multilayer printed circuit board, there is a method of a so-called build-up process which is carried out as follows: at first, forming a conductive pattern on an inner layer substrate, then forming an insulating layer on the inner layer substrate formed the conductive pattern, and then further forming a conductive pattern on the insulating layer. Repeating this process, a plurality of conductive layers are formed. However, the build-up process has disadvantage such that if any failure occurs with a layer, all layers will be defective, thus productivity decreases. Further, in the build-up process, it tends to produce a defective product due to cracking in an insulating layer because a heat compression is repeated for laminating substrates. To avoid this problem, there is another method in which a multilayer printed circuit board is manufactured by integrating a plurality of substrates. Each substrate having a conductive pattern thereon is made individually, and laminating them having the insulating layers therebetween to be integrated. In this method, a metal bump is formed integrally on a conductive pattern at a position where an interlayer connection is established on each substrate. A conductive paste is adhered to tips of the metal bumps so as to integrate substrates; at the same time, an interlayer connection is established by press-welding the metal bumps with the conductive paste at the position where the interlayer connection is established on other substrate.